Directory assistance systems incorporate a wide range of automation to reduce the cost of human operators. Almost all systems use custom database software to locate listings quickly.

Most directory assistance systems use automated readback systems to give out the phone number. This frees the directory assistance operator to move on to another caller as soon as the correct listing is located.

Some systems have "store and forward" technology which records "city and state" the caller is requesting and then plays the city and state speech to the operator before they come online and then say "Residential or business listing?" or simply "What listing please?"

Most systems recognize location and listing. If recognition confidence is high, the best result is played to the caller. If confidence is low, the caller's request is played back to a live operator, who locates the correct listing.

However, a 411 landline call will provide local listings as well as nationwide listings and sometimes international listings.

Most telephone companies permit up to two listings per 411 call. All wireless carriers offer nationwide listings with 411, and some offer additional Enhanced Directory Assistance services. However, wireless numbers for residential customers are not available via 411.

411 LDA: Local Directory Assistance. 411 is dialled and the operator is requested to search for a listing in a group of area codes "LATA" local to the caller. Example: the caller lives in area code 630 (Oak Brook, IL) and request a listing for a business in area code 312 (Chicago, IL). In this case, AT&T Illinois bills the call.

411 NDA: National Directory Assistance. 411 is dialled and the operator is requested to search for a listing in an area code not local to the caller. Example: The caller lives in area code 630 (Oak Brook, IL) and requests a listing for a business in area code 213 (Los Angeles, CA). In this case AT&T Illinois bills the call.

(area code) 555-1212: National Directory Assistance. This example assumes the caller is in Oak Brook, IL (area code 630) and uses Verizon as their long distance carrier. Example: The caller is looking for a listing in Los Angeles, CA (area code 213) and dials 213-555-1212. In this case Verizon bills the call.

In the U.S., directory assistance for companies with toll-free "800 numbers" (with area codes 800, 844, 855, 866, 877, and 888) is available from toll-free directory assistance.

Toll-free directory assistance is provided by telecommunication providers, namely AT&T and Verizon, as mandated by the Federal Communications Commission. Companies must request to have their toll-free number listed and pay the providers each time their phone number is released to a Toll-free directory assistance caller. In 1999, AT&T applied for permission to discontinue this service[2] but it remains active.

The services of 4-1-1 queries is often outsourced to a call centre that specializes in that function. Historically, when a single carrier provided most of the telephony services for a region, the data used to satisfy the search could come exclusively from that carrier's subscriber rolls. Today, when the market is fragmented amongst many carriers, the data must be aggregated by a data aggregator specializing in directory listings, such as LSSi. The data aggregator distributes the data to the 4-1-1 services either on a "live" basis, actually servicing each query, or by periodically transferring large swaths of listings to the call center's systems for local searching or for online directory assistance searching at 411 directory assistance.

The data aggregator collects the data from the rolls of many telecommunication carriers. Some carriers such as Vonage do not send their customer rolls to the aggregator. Their customers can get their listings in the directory assistance database using a free service such as ListYourself.net.

Recently private companies have entered the directory assistance market by offering free directory assistance. Customers often must listen to an advertisement prior to receiving directory services.[3] In Canada, free Local and National Directory Assistance service for business and residential listings is available online by 411 Directory Assistance Canada.[4]

In the United Kingdom, directory assistance is called directory enquiries.

Directory enquires is provided by a variety of different companies, with a variety of call charges, each company reached by dialling a six-digit number beginning with 118. These companies supply information from the Operator Services Information System (OSIS), which is run by Directory Solutions, a division of BT Wholesale. OSIS accepts updates from telecoms providers seven days a week, and supplies that information to the enquiry companies six days a week.[5] There are currently over 200 providers.[6] Four of these, 118 118 (The Number), 118 212 (Maureen), 118 247 (Yell) and 118 500 (BT) are among the most expensive and yet have over 90% of the market, mostly due to heavy advertising.[citation needed]

Directory enquiries used to be reached by dialling 192 (domestic numbers) or 153 (foreign), with the service supplied by the telephone company providing the fixed or mobile service to the calling telephone. Historically the service was free at the point of use. During the 1990s charges were brought in to use this service from home or business lines, although for some years after Directory Enquiries were free from payphones. These numbers were switched off on 24 August 2003 following the introduction of competition to directory enquiries.

The pricing structure for UK directory enquiries was reformed by Ofcom on 1 July 2015.[7] Call charges consist of an Access Charge and a Service Charge. The Access Charge is set and retained by the caller's landline or mobile provider. The Service Charge is set by the directory enquiries service but it is collected by the caller's phone provider and then passed on to the directory enquiries service.

The Access Charge is set at a per minute rate and is typically 2p to 13p per minute from landlines or 5p to 55p per minute from mobiles. The Access Charge is always the same rate as applies for calls to 084, 087 and 09 numbers and must be shown prominently in tariff lists.

The Service Charge may be charged per call, per minute, or a combination of the two. The per-call part may be anywhere from 5p to £16 and applies as soon as the call is answered. The per-minute part may be anywhere from 1p to £8 and may apply from the start of the call or may apply after the first 60 seconds has elapsed. There are 100 available Service Charge price points, known as SC001 to SC100.[8][9] The Service Charge must be declared alongside the number wherever it is advertised or promoted.[10]

The applicable Service Charge codes are also shown in BT's pricing table section 2, part 15.[11] Having found the "SC" code for a particular number, it is then necessary to refer to part 19 to find the cost.[12]

A number offering a directory enquiries service allowing people to request to be put through to a mobile phone number was established in June 2009.[13] 118 800 proved to be controversial, however, when it was revealed that it was making available 15 million mobile numbers that it had bought from market researchers.[14] Its website was suspended[15] within weeks of its launch so that the company could re-engineer the site to enable the large number of ex-directory requests to be handled more efficiently.[14] As of 2017[update] the 118800.co.uk site remains non-functional.

In 2014, the 118500 service run by BT was fined £225,000 by PhonepayPlus (now renamed as the Phone-paid Services Authority) for over-charging customers and failing to clearly display call costs.[16] BT were also ordered to refund affected customers.

Later in 2014, a similar failure to clearly state call costs resulted in a fine for the 118118 service.[17][18]

In 2017, soaring call costs for directory enquiries services including 118118 and 118500[19] prompted an Ofcom review of 118 services.[20][21][22]

Some directory enquiries services stand accused of inappropriate methods of promoting their services, effectively scamming people into calling. Various unallocated geographic and non-geographic numbers play an announcement directing callers to call a particular directory enquiries number for help. People may hear this message when they mis-dial a wanted number[23] or may appear to have missed a call from the unallocated number and hear this message if they call back.